PURPOSE: To determine the clinical and mammographic characteristics of primary lymphoma of the breast. MATERIALS AND METHODS: The clinical and mammographic records of five patients (six breasts; bilateral involvement in one patient) with histologically-proven lymphoma of the breast were retrospectively reviewed. RESULTS: All patients had complained of a palpable tender mass with relatively rapid growth over a period of about 3 months. In five cases, the mass was located in the right breast and in one case in the left. Mammography revealed diffuse increased opacity of the entire breast in three cases, a homogeneous well-defined mass in one, multiple well-defined masses in one, and ill-defined lobulated opacity in one. Skin thickening and architectural distortion was seen in one case, and axillary lymphadenopathy in two. In no case was microcalcification and nipple retraction seen. CONCLUSION: In primary breast lymphoma, mammographic finding are non-specific. When a breast grows rapidly and is tender, however, and mammography shows a relatively large well defined mass and associated axillary lymphadenoapathy, the possibility of primary lymphoma should be considered.